From what I understand, Arche essentially means 'beginning'. According to Greek philosophy, the arche is where everything originated and also where it will end. It was first theorized by Thales that water was the basis of all things, supported by the observation that moisture could be found throughout the entire world. However, this theory was refuted by his successor, Anaximander, who stated that water couldn't produce it's opposite -- fire. Anaximander proposed the idea of an indefinite substance as the arche, called apeiron. Following the pattern, Anaximenes, who was Anaximander's student, proposed a theory which stated that air is the arche, rather than an indefinite substance. Anaximenes observed that decreasing the density in air (or rarefaction) creates fire, which can become water and eventually, stone (earth).
From what I understand, Arche essentially means 'beginning'. According to Greek philosophy, the arche is where everything originated and also where it will end. It was first theorized by Thales that water was the basis of all things, supported by the observation that moisture could be found throughout the entire world. However, this theory was refuted by his successor, Anaximander, who stated that water couldn't produce it's opposite -- fire. Anaximander proposed the idea of an indefinite substance as the arche, called apeiron. Following the pattern, Anaximenes, who was Anaximander's student, proposed a theory which stated that air is the arche, rather than an indefinite substance. Anaximenes observed that decreasing the density in air (or rarefaction) creates fire, which can become water and eventually, stone (earth).